Trade union membership, UK, 1995 to 2025: technical information
Published 28 May 2026
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This publication is available at https://www.gov.uk/government/statistics/trade-union-statistics-2025/trade-union-membership-uk-1995-to-2025-technical-information
Technical information related to the trade union membership statistics publication that remains unchanged from previous years is set out in the Technical Information for the 2024 bulletin.
The information covered includes:
- trade union questions in the Labour Force Survey (LFS)
- Northern Ireland 1997 data issue
- variables in the LFS
- switch from seasonal to calendar quarters
- estimating union membership levels
- differences between administrative data and LFS estimates
Updated information for the 2025 bulletin is shown below.
Sample size and standard errors
This publication has changed its approach to publishing data where cell sizes may not provide reliable estimates to reflect current Office for National Statistics (ONS) guidance on Measuring and reporting reliability in the Labour Force Survey and Annual Population Survey.
This states that, for consistency over time, the reliability thresholds should be set on the unweighted cell size for the category being estimated, and the ONS recommend that figures based on unweighted cell sizes of 26 or above will pass their quality threshold. Figures based on unweighted cell sizes of 3 to 25 should be shaded to reflect that they are likely to have a higher coefficient of variation than required to meet the threshold. Figures based on cell sizes of under 3 should not be published to protect against the risk of disclosure, and in this publication have been marked with a [U].
As an indication of the standard errors in the trade union estimates, the standard errors around the total employment and employee union membership proportions are likely to be around 0.3 percentage points for 2025. Standard errors for union membership proportions by gender are likely to be around 0.4 percentage points. Standard errors for union membership proportions by region average around 0.9 percentage points.
The 95% confidence intervals for trade union membership, presence in the workplace, collective agreements and average wages are provided alongside the tables. These have been calculated using the survey package in R following ONS guidance on calculating confidence intervals for complex survey designs such as the LFS.[footnote 1]
Following the guidance provided by the LFS methodology team, the person identifier (CASENO) is used as the clustering variable, unitary authority/local authority (UALA) as the low-level geography stratum, and the person weight (PWT) and income weight (PIWT) as the weighting variable where applicable. As with the tables, the domain is employees or those in employment that are not in a military occupation.
Annual Survey of Hours and Earnings (ASHE)
The Annual Survey of Hours and Earnings (ASHE), conducted by the ONS collects information on the number of employee jobs where pay is set with reference to an agreement affecting more than one employee (such as agreed collectively by a trade union or a workers’ committee). The question asked is therefore broader than that asked in the LFS. As the information is collected from employers it may give a more accurate picture of the coverage of such agreements. The achieved sample in 2025 was around 174,000.
In this bulletin, the ASHE figures relating to collective agreements have been included in the main tables and are used as the main measure of collective agreement coverage. We expect the figures more reliably reflect the level of coverage in the UK.
It is known from surveys of employers that only a small proportion of public sector workplaces are not covered by collective bargaining, and that these arrangements are generally made at head office level or across many organisations. It is therefore likely that some employees who are not union members or who work in small workplaces in the public sector may be unaware that collective bargaining arrangements apply to their organisation.
There is potentially a similar effect among workers in the private sector. This may explain why the LFS estimate of collective bargaining coverage is below the expected level, especially for the public sector. In addition, because sector is self-reported in the LFS, there may be a number of respondents wrongly classifying themselves as public sector workers. Consequently, there may be a downward bias to this measure.
The ASHE question references collective agreements agreed by a trade union or worker’s committee, so possibly some non-union collective agreements may also be included (though we would not expect these to be widespread). The question in the LFS specifically refers to negotiations between the employer and a trade union that affect an employee’s pay and conditions. The LFS collective agreements statistics are provided in the annex tables.
Transformed Labour Force Survey (TLFS)
Due to quality issues with the LFS, linked to response rates and achieved sample falling substantially during the COVID-19 pandemic of 2020, ONS has been developing a Transformed Labour Force Survey which will be an online-first version of the LFS, with a much larger initial sample. It has subsequently been split into a shorter ‘core’ survey and a longer ‘plus’ version.
A decision on moving to the TLFS as the government’s main labour market survey in November 2026 will be taken in July 2026. However, ONS has stated that its current assessment is that further assessment and data collection will be necessary before the TLFS can be assessed as ready to replace the LFS, and the transition to the TLFS will move to 2027. The trade union questions will be included in the ‘plus’ survey. Labour market transformation – update on progress and plans - Office for National Statistics
The introduction of the TLFS could lead to changes to the figures in the bulletin. Next year’s bulletin may also be affected by a larger re-weighting of the LFS going further back than the most recent years to reflect changes to estimated population trends influenced by the 2021 Census.